aspnetcore: Controller.ViewComponent is not async

Is there an existing issue for this?

I have searched the existing issues

Describe the bug

Controller.ViewComponent writes synchronously to the HttpResponseStream if the content of the component is large enough causing the "System.InvalidOperationException: 'Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true "

Calling the same view from the controller with Controller.PartialView and the path to the component view or creating a wrapper view that calls @await Component.InvokeAsync avoids the issue. There are no synchronous renderpartial or partial calls in the view. The response size is 25kB.

This is the call stack of the exception:

   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 count)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternal(Boolean flushEncoder)
   at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(String value)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.Buffers.ViewBuffer.<WriteToAsync>d__23.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewComponentResultExecutor.<ExecuteAsync>d__7.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewComponentResultExecutor.<ExecuteAsync>d__7.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<<InvokeNextResultFilterAsync>g__Awaited|30_0>d`2.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<<InvokeResultFilters>g__Awaited|28_0>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<<InvokeNextResourceFilter>g__Awaited|25_0>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<<InvokeFilterPipelineAsync>g__Awaited|20_0>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<<InvokeAsync>g__Logged|17_1>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<<InvokeAsync>g__Logged|17_1>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<<Invoke>g__AwaitRequestTask|6_0>d.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Session.SessionMiddleware.<Invoke>d__8.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Microsoft.AspNetCore.Session.SessionMiddleware.<Invoke>d__8.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Authorization.Policy.AuthorizationMiddlewareResultHandler.<HandleAsync>d__0.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.<Invoke>d__6.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.<Invoke>d__6.MoveNext()
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

Example code with error:

        public virtual IActionResult DetailViewEdit(Dictionary<string, string> extraParam)
        {
            //DETAILVIEW
            var detailView = CreateViewEditInsertDetailView(ViewEditState.Edit, extraParam);

            return ViewComponent(ViewStrings.Components.DetailView, detailView);
        }

No error:

        public virtual IActionResult DetailViewEdit(Dictionary<string, string> extraParam)
        {
            //DETAILVIEW
            var detailView = CreateViewEditInsertDetailView(ViewEditState.Edit, extraParam);

            return PartialView(ViewStrings.Components.ComponentWrapperPath, new ComponentWrapperModel { Component = ViewStrings.Components.DetailView, Model = detailView });
        }

wrapper view:

@model ComponentWrapperModel

@await Component.InvokeAsync(Model.Component, Model.Model)

No error 2:

        public virtual IActionResult DetailViewEdit(Dictionary<string, string> extraParam)
        {
            //DETAILVIEW
            var detailView = CreateViewEditInsertDetailView(ViewEditState.Edit, extraParam);

            return PartialView("/Views/Shared/Components/DetailView/_Default.cshtml", detailView);
        }

Expected Behavior

As visible from the call stack ViewBuffer.WriteToAsync calls the Stream.Write method instead of Stream.WriteAsync. Why this only happens by calling Controller.ViewComponent I am not sure.

Steps To Reproduce

No response

Exceptions (if any)

System.InvalidOperationException: 'Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true

.NET Version

.net6

Anything else?

.NET SDK (reflecting any global.json): Version: 6.0.101 Commit: ef49f6213a

Runtime Environment: OS Name: Windows OS Version: 10.0.19043 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\6.0.101\

Host (useful for support): Version: 6.0.1 Commit: 3a25a7f1cc

.NET SDKs installed: 2.1.201 [C:\Program Files\dotnet\sdk] 2.1.202 [C:\Program Files\dotnet\sdk] 2.1.300 [C:\Program Files\dotnet\sdk] 2.1.401 [C:\Program Files\dotnet\sdk] 2.1.402 [C:\Program Files\dotnet\sdk] 2.1.526 [C:\Program Files\dotnet\sdk] 2.1.818 [C:\Program Files\dotnet\sdk] 2.2.103 [C:\Program Files\dotnet\sdk] 2.2.401 [C:\Program Files\dotnet\sdk] 2.2.402 [C:\Program Files\dotnet\sdk] 3.1.417 [C:\Program Files\dotnet\sdk] 5.0.104 [C:\Program Files\dotnet\sdk] 5.0.404 [C:\Program Files\dotnet\sdk] 5.0.406 [C:\Program Files\dotnet\sdk] 6.0.101 [C:\Program Files\dotnet\sdk]

.NET runtimes installed: Microsoft.AspNetCore.All 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.1.30 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.All 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All] Microsoft.AspNetCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.2 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.1.30 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.22 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 3.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 5.0.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.AspNetCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App] Microsoft.NETCore.App 2.0.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.3-servicing-26724-03 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.1.30 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 2.2.8 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 3.1.23 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 5.0.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.NETCore.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App] Microsoft.WindowsDesktop.App 3.1.22 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 3.1.23 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.13 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 5.0.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App] Microsoft.WindowsDesktop.App 6.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

About this issue

Original URL
State: open
Created 2 years ago
Reactions: 2
Comments: 36 (16 by maintainers)

Commits related to this issue

Add `AbpMemoryPoolHttpResponseStreamWriterFactory`. https://github.com/dotnet/aspnetcore/issues/40928 — committed to abpframework/abp by maliming a year ago

Most upvoted comments

I’ve managed to create a simple reproduction. It has to do with the length of content returned.

That’s right, It’s related to the length of the view content.

maliming on Aug 15, 2022

It seems some work has been done regarding this issue on the Blazor side #49172 . Will this be ported to asp.net core?

primozcerar on Oct 30, 2023

And that is the problem that needs to be solved.

primozcerar on Mar 1, 2023

@TanayParikh can you please investigate this and summarize your findings and any actions to be taken for resolving this issue? Thanks!

mkArtakMSFT on Nov 1, 2022

I’ve come across this issue too.

I’ve managed to create a simple reproduction. It has to do with the length of content returned.

namespace WebApplication1.Controllers;

using Microsoft.AspNetCore.Html;
using Microsoft.AspNetCore.Mvc;

public class HomeController : Controller
{
    public IActionResult Index()
    {
        return this.ViewComponent(typeof(WorkingViewComponent));
    }

    public IActionResult Fail()
    {
        return this.ViewComponent(typeof(FailingViewComponent));
    }
}

public class WorkingViewComponent : ViewComponent
{
    public IHtmlContent Invoke()
    {
        return new HtmlString(new String('X', 15000));
    }
}

public class FailingViewComponent : ViewComponent
{
    public IHtmlContent Invoke()
    {
        return new HtmlString(new String('X', 20000));
    }
}

Version: 6.0.302 Commit: c857713418

psylenced on Aug 1, 2022

@kjbetz @MisinformedDNA I have ran into this issue as well with Blazor .NET 8 preview 6. If the body contains too much text, the page won’t load and it throws an error. I created a separate issue for this here (before I saw your comments): https://github.com/dotnet/aspnetcore/issues/49466

lanedirt on Jul 17, 2023

Yep, I have a Blazor 8 (preview 6) page with static HTML and if there’s “too much” text, I get the error. Reducing the text size fixes it. It’s not even that much text! How do I get Blazor to work? this is a very simple app that Blazor should easily be able to support. @mkArtakMSFT @danroth27

MisinformedDNA on Jul 17, 2023

I believe I’m also encountering this issue as well.

I’m attempting to use ASP.NET Core 8 Preview 5 with the new Blazor full-stack / SSR. I have a page that just has static HTML in it (a privacy page.) Formatted HTML is about 460 lines. I get this error. If I lower the lines to around 240 the page loads showing about 16kb data from this page.

Is this the same issue? Is there a work around?

kjbetz on Jun 19, 2023

That is not a solution in my opinion. It should be async but it isn’t.

primozcerar on Mar 1, 2023

I think I’m hitting exactly the same issue. Invoking a VC directly from a Controller action method using
return ViewComponent(…

crashes with error

System.InvalidOperationException: Synchronous operations are disallowed. Call WriteAsync or set AllowSynchronousIO to true instead. at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpResponseStream.Write(Byte[] buffer, Int32 offset, Int32 count) at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.FlushInternal(Boolean flushEncoder) at Microsoft.AspNetCore.WebUtilities.HttpResponseStreamWriter.Write(String value)

It works fine most of the time, but in one specific case the view component returns html containing a large json object - in this case data for a Kendo dropdown list which contains nearly 1000 items.

I’m sure there are work-rounds for this - e.g. enabling synchronous IO, but that’s not the point.

robinsmh on Jun 29, 2022

@primozcerar the comment our bot made might not be completely accurate in this case. This is simply part of our planning process, we are acknowledging that there is very likely an issue here. However an engineer from our team needs to spend time looking at it to understand the details and produce a detailed explanation of what’s going on before we decide whether this is a bug, a bad design or a technical limitation and then decide what next steps we should take.

javiercn on Apr 5, 2022

@welshronaldo Thank you for this. I appreciate it since I couldn’t reproduce the issue in a simple project. Hopefully this helps solve it.

Edit: Your repro project seems to show the same issue judging from the call stack of the exception. I even tried to change the TestComponent.cs in your project to use InvokeAsync just in case that changes anything but the exception remains.

primozcerar on Apr 5, 2022